Process of treating photographic layers containing color formers with metal salt hardening agents



Patented Dec. 12, 1950 PROCESS OF TREATING PHOTOGRAPHIC LAYERS CONTAINING COLOR FOEMERS WITH METAL SALT HARDENING AGENTS Otis Willard Murray, Fords, N. J., assignor to E. I. du Pont de Nemours & Company, Wilmington, Del., a corporation of Delaware No Drawing. Application June 11, 1946, Serial N0. 676,090

Claims. 1 This invention pertains to color photography and, more particularly, to processes of color photography utilizing color formers in colloid layers. Still more particularly it pertains to the surface hardening of colloid layers containing color formers and to the color coupling development of exposed photographic elements hearing such layers.

Processes of producing colored images utilizing color formers, such as phenols, naphthols, reactive methylene compounds, and aromatic amino developing agents, have been known for many years. Such processes are described in Fischer United States Patent 1,102,028. The specific color formers described in this patent have relatively low molecular weight and tend to diffuse in gelatin silver halide layers when such layers are subjected to prolonged treatment in aqueous treating baths and especially in reversal color coupling development procedures. Fischer proposed to reduce the diffusion of the color formers by tanning photographic silver halide emulsions. It has been found that the addition of tanning or hardening agents to silver halide emulsions which contain color formers does not solve the problem because layers cast from the emulsions still exhibit considerable diffusion of the color formers upon colorcoupling development.

An object of this invention is to provide processes of color photography which utilize migratory color formers in emulsion layers. A related object is to provide methods for reducing the migration of color formers in and from thin colloid layers. A still further object is to provide a simple and economical method for reducing the migration of color formers in colloid layers. Another object is to provide means for utilizing color formers of migratory type in colloid layers. Still other objects will be apparent from the following description of the invention.

It has been determined that color formers which possess a moderate to low rate of diffusion in thin colloid silver halide emulsion layers and, more particularly, gelatino-silver halide emulsion layers can be made markedly more resistant to diffusion if the wet layers are given a hardening treatment with an aqueous solution containing certain types of hardening agents and a wetting agent. This may be advantageously accomplished by applying to the wet gelled surface of the colloid layer, e. g.. a gelatino-silver halide emulsion layer, a concentrated aqueous solution of a polyvalent metal salt gelatin hardening agent which contains a small amount of a hydrotropic wetting agent at a temperature below the set- 2 ting point of the colloid. The layers are dried and then can be exposed and color developed by a direct coupling procedure.

In the case of multilayer films which are differentially sensitized so as to record in the different primary color regions of the spectrum and contain color formers which yield dyes complementary in color to the utilized sensitivity of the spectrum, the respective layers should be superhardened after each coating operation.

The hardening treatment may be accomplished by the usual coating methods for nonviscous liquids, for example, by applying the hardening solution from a hopper through an openin of narrow cross-section or by means of transfer or beading rollers, dipping, spraying, etc. onto the surface of the wet gelled emulsion layer.

The amount of hardening agent used in the treating solution may vary quite widely but the amounts used are preferably considerably in ex-. cess of those used in hardening or tanning gelatin silver halide emulsions. A preferred range of amounts is from 2 to 30 grams per liter of solution. The amount of hydrotropic agent may also vary. A practical range is from 0.05 to 2% by weight based on the amount of water.

The invention will be further illustrated but 'is not intended to be limited by the following examples.

Example I f A transparent cellulose acetate film base support was coated with an mg. of silver bromide per square decimeter coating weight of a gelatinosilver halide emulsion containing one gram of l-meta amino phenyl-3-methyl-5-pyrazolone per five grams of gelatin. To the surface of the wet, gelled emulsion was applied the following solution at room temperature:

Water m cc 6000 Chrome alum grams 5% saponin cc 250 veloper contamination caused by leaching of the color intermediate showed considerably less migration from the film on the treated sample than on the untreated.

Example If A cellulose acetate film base Was coated with a 40 mg. of silver bromide per square decimeter a positive type gelatino-silver halide emulsion layer containing one gram of l-meta amino phenyl-3-methyl-5-pyrazolone.

The outer layers were then treated by applying a solution of the following composition;

Water grams 5000 Chrome alum do 100 Saponin (5% aqueous) cc 500 Sodium dodecyl sulfate aqueous) cc After one week aging at room temperature, the film was exposed to two suitable separate negatives and then developed in a solution of the composition:

Diethylparaphenylene diamine HC1 grams 2 Sodium sulfite (anhydrous) do 5 Sodium carbonate (anhydrous) do 20 Water to liter 1 It was found that a considerable footage of cine film could be developed without any significant contamination of the developer solution. A third color may be applied to the hardened emulsion surface by any conventional imbibition method.

The expression color former as used herein has the'well-established meaning in the art and refers to organic compounds which are capable of coupling with oxidized primary aromatic developing agents to form quinoneimine or azomethine dyes. I Such compounds are also capable of condensation or coupling with diazotized aromatic amines to form azo dyes. Color formers usually contain as the active group a structure which may be represented by the formula:

where X is H0- or RHN- or an aliphatic or substituted aliphatic group, and n is 0 or 1. The free or danglingdvalences may be, of course, satisfied by any of a large number of atoms or groups, e. g., hydrogen, halogen, carboxylic or sulfonic acid groups and their derivatives, fused rings, alkyl, aryl, alkoxy, arloxy, etc. The hydrogen atom in the formula may be replaced by groups readily displaced in the coupling reac- 'tlon, e. g., halogen atoms, carboxylic or sulfonic acid groups. This group is found in the reactive methylene dye intermediates and in aromatic hydroxyl and amino compounds and includes the reactive ethanol, aminoethenyl, 4-hydroxyand 4-amino-1,3-butadienyl groups. These groups occur, in phenols, naphthols, aromatic amines, acylacetamides, beta-keto-esters, pyrazolones, homophthalimides, cy'anoacetyl compounds, etc. A large number of suitable mobile color formers are described in the British Journal of Photography, pages 647 and 648, for October 14, 1938. This article also discloses a large number of primary aromatic amino color developing agents which can be used in processing the elements described therein. l, v r

The reactive ethanol group :as represented by I ETD-0:011-

occurs in phenols and naphthols which couple in the ortho position and in the alkali soluble or enol form of most reactive methylene dye intermediates. These reactive methylene groups have a hydrogen rendered mobile by the proximity of certain unsaturated groups, such as, for example, NO2,

and others. The CH2 group is usually present between two such groups, for example,

COCH2CO-, -COCH2CN, -COCH2C=N in a cyclic or acyclic system. The enol forms of these examples are and H0 C=CHL|?=N respectively.

The reactive amino ethenyl group occurs in aromatic amino compounds which couple in the ortho position.

The 4-hydroxyand 4-amin0-l,3-butadienyl groups represented as RHN-(IJ=JJ(=CH occur in phenolic, naphtholic, and aromatic amino compounds which couple in the para position.

The colloid silver halide emulsion layers may contain, in addition to the light-sensitive silver halide, e. g., silver chlorides, silver-chloridebromide, silver-iodobromide, etc., various sensitizing dyes and other materials which are common in emulsion layers. Such additional materials include fog inhibiting agents, emulsion hardeners, emulsion preservatives, etc.

In place of the specific hydrotropic wetting agents described above, there may be substituted one or more other agents of this kind. Suitable ones include sodium octodecyl sulfate, potassium tetradecyl sulfate, n-cetane sulfonic acid ammonium salt, the diethylcyclohexylamine salt of stearic, palmitic, etc. acids, alkali metal salts of alkylated aromatic sulfonic acid, e. g., the sodium and potassium salts of tri-isopropylnaphthalene sulfonic acid, dimethylnaphthalene sulfonic acid,

etc. Still other hydrotropic agents are described in Ullman Encyclopedic der Technischen Chemie, 2nd edition, vol. IX, page 808. The alkali metal sulfates of alkanols of 12 to 18 carbon atoms are especially useful.

Suitable additional trivalent metallic salt hardening agents comprising trivalent metallic salts of chromium, aluminum, and iron which can be used in place of chrome alum include chromic bromide, chromic sulfate, aluminum chloride, potassium alum, ferric chloride, and ferric sulphate.

The invention is especially useful with hydrophilic protein colloid binding agents, such as gelatin, casein, and zein but is not limited to that type of binding agent. Among the useful binding agents are hydrophilic hydroxyl polymers, including polyvinyl alcohols, partially hydrolyzed polyvinyl esters, e. g., polyvinyl acetate, polyvinyl chloracetate, and polyvinyl isobutyrate which contain a large number of free hydroxyl groups,

hydrolyzed ethylene/vinyl acetate interpolymers of the type described in United States Patent 2,386,347, cellulose derivatives, e. g., low substituted cellulose acetate and methyl cellulose and super polyamides as described in United States Patent 2,384,072.

The invention may be used in various kinds of photographic elements for the production of colored images including single and multilayer films,

plates, and papers.

An advantage of the invention is that it provides a practical method of improving the resistance to diffusion of color formers. Those which have a moderate to low rate of diffusion are rendered relatively fast to diffusion by the process. The lower molecular weight color formers which may be used in this process are simple to synthesize and render the process more economical.

As many widely different embodiments of this invention can be made without departing from the spirit and scope thereof, it is to be understood that the invention is not to be limited except as defined by the claims.

What is claimed is:

1. The process which comprises treating a wet photographic element prior to exposure with an aqueous solution containing from 2 to 30 grams per liter of solution of a polyvalent metal salt hardening agent and from 0.05 to 2.0% by weight, based on the amount of water, of a hydrotropic wetting agent, said element having a hydrophilic colloid silver halide emulsion layer containing a color former having as the active group a structure of the formula X c=( 1)flc=cH- where X is a member taken from the group consisting of HO- and HzN- and n is a cardinal number from to 1.

2. The process which comprises treating a wet photographic element prior to exposure with an aqueous solution containing from 2 to 30 grams per liter of solution of a polyvalent metal salt hardening agent and from 0.05 to 2.0% by weight, based on the amount of water, of a hydrotropic wetting agent, said element having a gelatin silver halide emulsion layer containing a migratory color former having as the active group a struc- 50 ture of the formula X- =o),.--d=cH-- where X is a member taken from the group consisting of HO- and H2N- and n is a cardinal number from 0 to 1.

3. The process which comprises treating a wet photographic element prior to exposure with an aqueous solution containing from 2 to 30 grams per liter of solution of a polyvalent metal salt hardening agent, saponin and from 0.05 to 2.0% by weight, based on the amount of water, of a hydrotropic wetting agent, said element having a gelatin silver halide emulsion layer containing a migratory color former having as the active group a structure of the formula X- ;=(t)n( :=oH-

where X is a member taken from the group consisting of HO and H2N and n is a cardinal number from 0 to 1.

4. The process which comprises treating a wet photographic element prior to exposure with an aqueous solution containing from 2 to 30 grams per liter of solution of a polyvalent metal salt hardening agent, saponin and from 0.05 to 2.0% by weight, based on the amount of water, of an alkali metal alkyl sulfate of 12 to 18 carbon atoms, said element having a gelatin silver halide emulsion layer containing a migratory color former having as the active group a structure of the formula X d=( :=ci1- where X is a member taken from the group consisting of HO and H2N and n is a cardinal number from 0 to 1.

5. A process as set forth in claim 4 wherein said polyvalent metal salt is chrome alum andsaid color former is l-meta-aminophenyl-3-methyl-5-pyrazolone and said alkyl sulfate is sodium dodecyl sulfate.

OTIS WILLARD MURRAY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,055,155 Fischer Mar. 4, 1913 2,367,548 Vittum Jan. 16, 1945 2,428,208 Edgerton Sept. 30, 1947 FOREIGN PATENTS Number Country Date 541,558 Great Britain Dec. 2, 1941 

1. THE PROCESS WHICH COMPRISES TREATING A WET PHOTOGRAPHIC ELEMENT PRIOR TO EXPOSURE WITH AN AQUEOUS SOLUTION CONTAINING FROM 2 TO 30 GRAMS PER LITER OF SOLUTION OF A POLYVALENT METAL SALT HARDENING AGENT AND FROM 0.05 TO 2.0% BY WEIGHT, BASED ON THE AMOUNT OF WATER, OF A HYDROTROPIC WETTING AGENT, SAID ELEMENT HAVING A HYDROPHILIC COLLID SILVER HALIDE EMULSION LAYER CONTAINING A COLOR FORMER HAVING AS THE ACTIVE GROUP A STRUCTURE OF THE FORMULA 